Generally, vehicles that use LPG for fuel are configured to inject gaseous LPG into the engine, in which LPG is provided by the fuel tank and is turned into gas by passing through the vaporizer and mixer. However, the LPG engine has drawbacks in terms of the engine output function, fuel economy, vehicle start at a low temperature, exhaust gas and the like. Therefore, LPI engine vehicles have been developed and used recently.
LPI engine vehicles are configured to compressively transfer LPG fuel to an injector through the fuel line by using a fuel pump installed in the fuel tank. Next, the injector injects fuel into the engine in a liquid state to improve engine output, fuel economy, vehicle start function at low temperatures, and exhaust gas emission levels.
In LPI engine vehicles, the fuel tank and regulator are each equipped with a shut-off valve, also called an isolating valve. If the LPG switch is turned off while the engine is running, the Interface Box (IFB) closes the isolating valves and stops the fuel flow from the injector.
Thus, in conventional LPI engine vehicles, when the LPG switch is turned off, the shut-off valves in the fuel tank and regulator are closed to stop the fuel supply. However, there is a drawback in that when the engine stops, the fuel pump continues to operate for a prescribed period of time by employing another power source, thereby causing an increase in noise and output consumption due to the unnecessary operation of the fuel pump.